Known optical sensor assemblies may comprise an aperture, a Fabry-Perot interferometer or etalon, and an optical sensor element. The term “optical sensor element” is used herein to designate an array of light-sensitive pixels, such as CMOS pixels.
The Fabry-Perot interferometer has a narrow transmission band, the center wavelength of which depends on its thickness. In the assembly described above, the purpose of the Fabry-Perot interferometer is to reduce the transmission of light onto the sensor outside the wavelength band of interest. The Fabry-Perot interferometer may have different properties (in particular, different thickness) for different corresponding regions of the optical sensor element, so as to obtain a multispectral or hyperspectral sensor assembly. An example of a hyperspectral sensor assembly obtained in this manner is disclosed in international patent application publication WO 2011/064403 A1. A further example of such a sensor assembly, combined with a second sensor element on the same substrate, is disclosed in international patent application publication WO 2011/073430 A1 in the name of the present applicant.
It is a disadvantage of the known optical sensor assemblies, that precise spectral characterization is a complex and time consuming task.